Stress is linked to increased risk of heart disease, depression, anxiety, diabetes, and suppressed immune function. Though decades of research have explored the biochemical makeup and the process of categorizing a stressful event, the specific cognitive mechanisms underlying stressful thoughts are not well understood. In the long run, understanding these mechanisms will inform how to measure, treat and ameliorate stress. Previous research has addressed cognitive mechanisms that may contribute to the experience of an event as stressful; namely, individuals become so immersed in the mental reenactment of stressful thoughts that the thought itself triggers a stress response and negative emotion. Mindful attention can prevent individuals from becoming immersed in the experience of stressful thoughts and setting off a stress response. Mindful attention involves recognizing one's thoughts are mental states that exist in one's mind, but not in the external world. When one treats thoughts this way, they arise and dissipate without a stress response. Currently, there is a lack of understanding about how preventing immersion in stressful thoughts through mindful attention reduces the individual's subjective experience of stress and its neural implementation. In an fMRI study, the present research aims to fill this gap by comparing neural activity when participants are fully absorbed in their thoughts about stressful scenarios (immersion perspective) to periods when they observe their thoughts as fleeting mental states (mindful perspective). This will shed light on cognitive mechanisms that contribute to mentally reenacting stressful events in thought. Researchers will also examine the neural underpinnings of reducing immersion in stressful thoughts. In addition, researchers will investigate how individual differences in trait absorption, rumination and mindfulness affect the tendency to become immersed in stressful thought. Participants who are more likely to ruminate or are higher in absorption may have more difficulty with mindful attention compared to those naturally high in mindfulness. Results of this project will increase our understanding of how to combat the negative effects of stress, how to treat stress related disorders, and how to identify persons at risk for stress related ailments, thereby potentially enabling prevention. This work may also shed light on the neural mechanisms of mindful attention and why there is a therapeutic effect of mindfulness-related treatments.